The invention is directed to a tube element, especially for exhaust systems and exhaust recirculation systems of combustion engines in vehicles, and more particularly to a tube element including a flexible hose made of metal having cylindrical end fittings, at least one helically or annularly corrugated bellows equipped with the cylindrical end fittings, and a braiding hose made of metal wire, which is fitted in a coaxial position to the bellows on its exterior surface. The bellows and the braiding hose are connected firmly and at least indirectly, and the inside diameter of the hose corresponds in general with the free outside diameter of the bellows.
The bellows are manufactured either absolutely tight from a pipe section or practically tight by means of helical winding of a pre-profilated metal strip. The tube elements are used for the purpose of absolutely or practically fluid-tight, particularly gas-tight, flexible connection with two pipe systems, each pipe system being connected with one end of a tube element and, in a special case, for the flexible connection within the exhaust system of a motor vehicle, where the tube elements are used for the purpose of allowing movement, especially of the engine, and for decoupling the engine vibrations from the passenger compartment.
In known tube elements, the exterior braiding hose is usually applied for the purpose of supporting the bellows against axial tensile stress. Designs have been developed in which existing tube elements do not have to carry out such axial support themselves as separate components of the exhaust system provide the needed support. As an example, existing tube elements have been installed before or behind catalytic converters, with the hoses being supported by suspensions. This allows the use of the braiding hose for other purposes, since it no longer has to carry out a supporting function.
In the case described above, however, the exterior braiding hose, which no longer guarantees an axial support, is situated at a distance from the bellows, with the exception at its end fittings, as the hose and bellows would be in direct contact at both end fittings. But over most of its length, the hose would be in a more or less variable position from the bellows. It is therefore unable to carry out other functions than those already mentioned. It is, in particular, unable to exert a direct influence on the vibrations of the bellows or on the functions of the tube element itself, which include the transfer of vibrations between the adjacent pipe systems as well as the damping of resonance vibrations by the bellows or the tube element. As a consequence of such vibrations, secondary acoustic effects may occur which could cause a disturbing sensation to the passengers of the vehicle.